1. Field of the Invention
The present invention relates generally to flanges for pipes and more specifically to a self-aligning flange for pipes and a large diameter extruded pipe.
2. Discussion of the Prior Art
Typically, attaching a flange to end of a pipe requires that the end of the pipe be substantially square to the length of the pipe. If the end pipe is not substantially square, the flange must be first tack welded to ensure squareness, before assembly welding. The “tacked-on” flange must be measured to ensure squareness and then the flange is fully welded to the pipe. The above process is time consuming and expensive.
Vacuum pipes for the sewer cleaning industry having a diameter of at least six inches in diameter and have always been rolled and seam welded. Seam welded pipes must be fabricated from an aluminum sheet material that is relatively soft to allow the aluminum sheet material to be bent into a round cross-section. A 3004H26 aluminum is typically used for seam welded pipe having at least an six inch diameter. The resulting surface hardness is 10–12 on a Rockwell “C” hardness scale. Further, the wall thickness of the six inch diameter seam welded pipe can only be 0.090 inches thick. Vacuum pipes are constantly exposed to banging and abuse and consequently do not last very long. 
Accordingly, there is a clearly felt need in the art for a self-aligning flange, which does not require an end of a pipe to be perfectly square to its length, nor does it require tack welding. There is also a clearly felt need in the art for a large diameter extruded pipe, which has a thicker wall and a harder exterior surface than that of the prior art.